A modified density gradient proteomic-based method to analyze endolysosomal proteins in cardiac tissue.

Area of Science:

• Cell Biology
• Proteomics
• Cardiovascular Science

Background:

• Lysosomes play crucial roles in cardiac physiology and pathology.
• Emerging evidence suggests lysosomal involvement in cardiac calcium signaling.
• Studying cardiac endolysosomal (EL) proteins is vital for understanding heart function and disease.

Purpose of the Study:

• To present a label-free proteomics method for analyzing EL proteins from small cardiac tissue samples.
• To enable detailed proteomic profiling of cardiac EL organelles.
• To provide a comprehensive dataset of EL organelle proteins in guinea pig atria.

Main Methods:

• Utilized density-separated fractionation (Percoll and sucrose gradients) to isolate EL organelles.
• Employed Western blot, enzyme activity assays, and liquid chromatography-tandem mass spectrometry (LC-MS/MS).
• Performed pathway analysis using KEGG, Reactome, Panther, and Gene Ontology.

Main Results:

• Successfully purified EL fractions with minimal contamination from sarcoplasmic reticulum or mitochondria.
• Identified a comprehensive set of EL proteins, including RAB proteins and lysosomal cathepsins (e.g., cardiac cathepsin D).
• Recovered significant catalytic activity proteins within the purified EL fraction.

Conclusions:

• The developed method is suitable for small cardiac biopsies, facilitating EL protein studies.
• The proteomic data provides insights into cardiac EL organelle composition and function.
• This technique is adaptable for EL organelle proteomics in various non-cardiac tissues.